My yr 2000 4x4 2500 chevy 6.0 gas tank makes a

Hi Larry:
Good observation. Not too many people would spot that.
When the engine is hot, the coolant is hot and expands. At the filler cap for the radiator, there will be a hose that goes to the overflow tank. As the coolant fluid expands, it flows through thie tube into the overflow tank.
When the engine is turned off, as it cools, the volume of coolant in the engine and radiator contracts, and is supposed to suck fluid back from the overflow tank.
I'm suspicious that something is preventing this from happening so the vacuum in the engine coolant system is collapsing the hose.
WHAT TO DO?
- Check the radiator cap. Make sure it is functioning correctly. Make sure that it is correctly installed and screwed all the way on.
- Check the coolant overflow hose. Make sure it is not plugged.
Odds are that you will find the problem quite quickly.
Cheerfuls.

Thats the evap system. The fuel tank has to deal with 2 types of pressure think of a gas can. Leave a 1/4 full gas can in sunlight it expands then leave it in the shade it contracts. There are preventive measure preventing the fuel tank from expanind and rupturing or imploding..The evap system is working

if its coming from the gas tank area the only thing i can think of would be the fuel pump..they make a little humming sound, but if its making a howling sound it might be going bad. does this help?

coolant expands and contracts. in the morning the coolant is contracted and is not makeing contact with the sencer in the resevior tank. fist thing in the morning top off your tank to the full mark

have your evaporative emission control system check.sound like you have purge valve solenoid not working or vent valve control solenoid.have it scan.to see which component not working..reason your gas tank expanding. your fuel vapor building up pressure.your purge valve and vent valve open allowing gas vapor from charcoil canister. to be burn in the intake manifold to be burn in combustion chamber.

It could just be the heat shield around your exhaust expanding and contracting again when your engine cools down. Sounds like a tin can type of popping noise?? If it is that's the heat sheild from the engine that protect's the spark plug wire and around under the truck cabin. Good luck and hope you find where the noise is coming from.

It sounds like the engine is pulling fuel from the tank, and not replacing it with air, causing a vacuum to build in the tank. The vacuum, may build to the point that it resists the fuel pump's efforts to **** fuel from it. If the vacuum is sufficient, it may collapse the tank, or expand the fuel enough for the engine manifold vacuum to **** raw gas into the evaporative emissions control system, hence the cannister.

Replacing the fuel pump, and filter will both break this vacuum, and make it run well for a few more miles, until the vacuum builds again.

The tank is usually vented to relieve pressure and vacuum through the gas cap.

Basically, sounds like a bad gas cap.

Try driving with the cap loose or removed. If that fixes it, buy a new cap. Preferably a locking one, as the amount of fuel these trucks hold is pretty tempting to less than honest folks. My 1990 C2500 has a 34 gallon tank.

Coil?? with the other symptoms, how'd you come up with that?

hi as for the fuel tank problem ? this is a vacumm problem created by the fuel pump workinh hard to draw fuel thus creating a vacuum inside tank suggest you ckeck the ventilation pipe from tank (under n/s/r wing along side filler pipe to see it is not kinked or blocked preventing tank to breath as pump draws fuel ?? as for excess fuel consumption? have you checked the air filter? remove it and check underneath ! this will give smoke you mention and you will have to press throttle more to overcome restriction air flow so more gas is more fuel used and little air to engine ? if you say engine stalls this is probably a result of tank vacuum and more fuel than air ?? hope this helps you sort it?

Sounds like something might be wrong with the charcoal canister. If not that, it's definalty something with the fuel evaporative system.

It is part of the waste gate just above the gas tank. It periodically checks for leaks and pressurizes and releases. Gives a ticking noise when it does this. Not a problem and GM is aware of this and said its normal on our cars.